Comment by FuriouslyAdrift

Loratadine plus famotidine worked for years for me (I have mastocytosis).

Switching to a keto diet helped way more, though. I still get flushes, rashes, etc., but the severity has gone down to the point they are random annoyances that go away as opposed to medical events.

Cromolyn and/or ketotifen are the big guns for mast cell disorders, though.